This invention relates to packaged stator core assemblies for dynamoelectric machines and more particularly, to a stator core assembly that rigidifies the stack of stator laminations and enables it to be easily and rigidly mounted within an associated housing.
Stator assemblies for dynamoelectric machines are either manufactured by stacking stator laminations in place in a suitable stator frame, or are made by completing a package of stator laminations and an associated stator winding, which is then mounted in operating position in a suitable frame. The former manufacturing method is generally used for various large machines where packaged stator assemblies are impractical due either to the size of the structure involved or due to the relative uniqueness of given stators for such machine sizes. Packaged stator core assemblies afford numerous manufacturing advantages, therefore, such assemblies are generally preferred and are frequently employed where the relative size and anticipated manufacturing volume of a given machine design justifies the use of such packaged cores. In addition to the cost savings and improved quality of manufacture that can be achieved by utilizing a packaged stator core assembly, it has been recognized that such assemblies can often be made tighter than stacked-in-place stator assemblies. Improved tightness of a stator assembly is particularly desirable where a dynamoelectric machine is to be applied in an environment that will subject it to seismic shock or other extreme mechanical vibrations that loosen the stator assembly and thereby impair its operating characteristics.
One form of a successful packaged stator core assembly design known in the prior art is disclosed in U.S. Pat. No. 3,940,648, which issued on Feb. 24, 1976 and is assigned to the same assignee as the present invention. The type of core packaging assembly illustrated in that patent has been found very suitable for use in the manufacture of horizontally mounted dynamoelectric machines because the stator-lamination clamping end flanges and the torque ribs of such a packaged stator assembly can all be welded to associated frame members of a rigid housing. Thus, the reaction torque developed in the stator laminations by operation of the machine are transmitted to the housing frame through the flanges and through intermediate so-called fishplate members that are welded between the torque ribs of the stator package assembly and intermediate housing frame plates. Although such a prior art packaged stator assembly is suitable for manufacturing horizontal machines, it is not ideally suited for use in the manufacture of vertical axis machines. In fact, due to the absence of core-to-frame connections between the stator clamping flanges of such vertical axis dynamoelectric machine housings, the use of stator core package assemblies such as those shown in the above-mentioned patent would not appear to be possible. The present Applicant is aware of only a few other types of packaged stator assemblies that have been used in manufacturing vertical axis dynamoelectric machines. These prior art packaged core arrangements use relatively flexible rectangular bars that are keyed to stator laminations and to clamping end flanges and the rectangular bars are welded directly to a housing frame. Such arrangements do not afford as tight and rigid a package core assembly and system for transmitting reaction torque from a vertically mounted core to a housing frame as does the present invention.
In addition to that shortcoming of known prior art packaged core assemblies, i.e., the inability to be utilized in the manufacture of a vertical-axis machine, the prior art packaged stator assemblies known to the Applicant have been found to possess other drawbacks. One of these drawbacks is that it is necessary to maintain access to the torque ribs of such stator cores after the cores are positioned within their housing frames, so that fishplates, which must be welded between the torque ribs of a given stator core package and the frame of its housing, can be welded in their operating positions. Thus, such assemblies are exposed to contamination from the manufacturing area until the access openings in the housings can be closed. In addition to such potential general housekeeping type of contamination of prior art stator assemblies, a considerable risk of further contamination to such stator assemblies exists due to the fact that the welding procedures for installing the needed fishplates inevitably creates a considerable amount of weld splatter and chip particles which may enter the stator air ducts or other portions of the stator package assembly. This further contamination problem is increased by the common need to apply multiple-pass fillet welds on the fishplates in order to make the welds of sufficient strength to resist the torque stresses that will be applied to them during operation of the machine. Because of such contamination problems it is always necessary to perform concomittant cleaning operations as a consequence of the use of such packaged stator assemblies, thus the cost of manufacture is increased. In addition, there exists the risk that all weld splatter particles and other contaminants may not be found and removed from the machine before it is put into operation. Finally, after such a machine has been cleaned, it is then necessary to close the access areas left in the housing in order to effect the needed fishplate welding operations. Typically, these access openings are closed by welding plates over them. Consequently, there is a further risk of weld splatter particles, resulting from such final welding operations, being splattered into the machine enclosure.
In addition to the foregoing disadvantages encountered in the use of known prior art packaged core assembly structures, it has been found that the extensive, relatively large welds needed to secure the torque ribs of such stator assemblies to the necessary fishplates and the housing frame members can cause thermal distortion of the frame. Moreover, the welded enclosure portions of such housings cannot be made as clean as the remainder of the housing bodies, which are typically shotblasted and painted prior to the closing welding operations. An undesirable corollary effect of welding the needed heavy fishplates between the torque ribs and a housing frame of such a prior art machine is that the overall weight of the machine is increased.